Building a Fence Around Partner
This was Board 1 from the 2025 USA Senior Team Trials Final:
| Vul:None Dlr: East |  K5 K1082 85 Q10987 | |
| Q7 AQ93 A1042 532 | 962 J7654 K763 6 | |
| AJ10843 -- QJ9 AKJ4 |
East dealt and passed and South opened 1
. West made a questionable (pushy?) A double to show the other suits takeout double and North showed clubs (via a 1NT transfer). East bid 2
and South made a An unusual jump showing 0-1 in that suit and support for partner Splinter Bid of 4. North's 4 bought the contract.
West astutely led a club; he expected his partner had shortness and might get a ruff(s). As you read the play to the first few tricks, try to decide what was a mistake and what was not.
Declarer won the 
A and played a spade to the king and a spade finesse to the jack, losing. West gave partner a ruff and East played a diamond to South's 
J and West's ace. This was the position:
| Vul:None Dlr: East | -- K1082 8 Q109 | |
| -- AQ93 1042 3 | -- J7654 K76 -- | |
| A1084 -- Q9 J4 |
West has to get this right to set the contract. The A would let declarer ruff and then throw both remaining diamonds (one on a club and one on the K). West must avoid trying to cash the A here to set 4. And what about declarer's play? IMHO, it was correct. Sure, we can see that banging down the high spades (as happened at the other table where E-W never bid) would mean 11 easy tricks. But with West's takeout double, declarer decided West was likely to hold spade shortness. Playing the A-K of spades would fail if East started with Q962. East would win the 3rd spade and cross in diamonds to get a ruff.
Given that declarer played correctly, should West figure out not to lay down the A at the key moment? Not really. If he trusts his partner, he should try to cash the A, playing for declarer to have started with:
AJ108434KJAKJ4K in the position shown. Then another diamond produced the setting trick, without West having to work up a sweat. If East doesn't play the K and West has faith in his partner, he should assume declarer has the K.